package exam.nio.T1;

import java.util.*;

public class Main {

    public static int n;
    public static int m;
    public static double[] prob = new double[] {0.8, 0.2};

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        n = sc.nextInt();
        m = sc.nextInt();
        System.out.printf("%.4f", solution());
    }

    private static double solution() {
        int s = n;
        double c = 1;
        for (int i=0; i<m; ++i) {
            c *= s;
            s--;
        }
        for (int i=1; i<=m; ++i) {
            c /= i;
        }
        for (int i=0; i<n-m; ++i)
            c *= 0.2;
        for (int i=0; i<m; ++i)
            c *= 0.8;
        return c;
    }
}
